Means for increasing the range of inductive train communication systems



May 1, 1951 P. N. OSSART 5 9 MEANS FOR INCREASI THE RANGE OF INDUCTIVE TRAIN COMMUNICATION SYSTEMS Filed Sept. 26. 1946 Raced 0191? .41 25 Aides. 25 Miles. 142

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I Hrs" ATTORNEY Patented May 1, 1951 MEANS FOR INCREASING THE RANGE OF INDUCTIVE TRAIN COMMUNICATION SYSTEMS Paul N. Bossart, Cheswick, Pa lassignor to The Union Switch & Signal Company, Swissvale, Pa., a corporation of Pennsylvania AppiicationSeptember 26, 1946, Serial No. 699,479

2 Claims.

My invention relates to means for increasing the'range of inductive train communication systerns, andimore particularly to meansfor increasing therange through which a wayside station can communicate with a train en route.

One service to be provided in communication systems, for trains and vehicles operating over atrackway, is that of communication between a wayside ,or t'erminal'station and the trains andlvehicle's en route. The rangeof transmission necessary for such communication varies reatly due to thechange in position of the trains on the traclgway.

liurthermcre the amount of power that can be sent out in inductive carrier communication systems may be limited due to government regulations and the range of transmission of the energy originally supplied by a transmitter may be insuflicient to reach vehicles at the more remote portions of the trackway.

Accordingly, a feature of my invention is the provision of improved means to increase the range of transmission of an inductive communicat o s m Another feature of my invention is the provision of improved means wherewith carrier communication energy is transferred from trans- Yfirse to longitudinal circuits of a pair of line wires and vice versa.

Almore specific feature of my invention is the provision of improved means for carrier inductive railway train communication systems wherewith a wayside station can communicate with trains operating over preselected sections of the track, without it being necessary to provide communication for all portions of the track. Other features, ,objects and advantages of my invention will appear as the specification progr sse To attain the foregoing features, objects and advantages of my invention, a pair of line wires extendingalong a trackway' over which trains and vehicles operate are usedin transverse and longitudinal circuits and means is provided, at preselected points to transfer the communicati'onenergy from the transverse to the longitudinal circuits and vice versa'.

The two line wires in parallel, their distributed capacitance and conductance to ground and the ground path form a so-called longitudinal circuit; and the line wires used in series forma so-called transverse circuit. I

The two line wires are mounted parallel to andjreasonably close to the track rails and their longitudinal .ci'r'cuitjis a part of a transmitting 2 channel which is inductively associated with vehicle carried circuits. The wayside station equipment is connected across the line wires to send and receive energy from the transverse circult. The electric and magnetic fields setup by the transverse circuit are relatively low compared to those for the longitudinal circuit and thus a larger power may be supplied to the transverse circuit without exceeding the socalled government low power rule limiting the field to 1. microvolts per meter at a distance normal to the line wires of an electrical radian, that is, about one-sixth of a wave length. Thus, according to my invention power at the wayside station is applied to the transverse circuit and a relatively large amount of power can be used without exceeding the low power rule. For example, a transmitter having an output capacity of approximately 50 watts must be limited to about 2 /2 watts if connected to a longitudinal circuit but can be operated to supply its full output when connected to the transverse circuit. When the power of the transverse circuit is attenuated to the level where the energy may be applied to the longitudinal circuit without exceeding the low power rule, the energy is transferred through proper apparatus. The energy is now transmitted in both directions from the transfer point and is available for influencing train carried circuits of any vehicle within the usual transmission range of the transmitting channel. In this way energy can be transmitted from a wayside station to preselected points and transferred to the longitudinal circuit for effective communication with trains for a distance each side of each transfer point equal to that which could be effected eachside of the wayside station when the power is supplied directly to the longitudinal circuit at thewayside station. When transmission is desired in one direction only from the transfer point, blocking means is provided in the line wires for the direction in which communication is not wanted. The equipment also works satisfactorily to increase the range of transmission from a train to the wayside station since the equipment at the transfer point is effective to transfer from the longitudinal circuit to the transverse circuit.

3 communication between a Wayside station and trains en route through a stretch of track extending in each direction from the wayside station. Fig. 2 is a diagrammatic view showing a form of apparatus embodying my invention when used with a railway train communication system that provides communication between a wayside station and trains operating over a preselected stretch of the track located to one side of the wayside station and remote therefrom.

t is to be understood that my invention is not limited to railway train communication systems nor to the two special arrangements here shown' and these are used to illustrate the many places the apparatus is useful.

In each of the two views like reference characters are used to designate similar parts.

Referring to Fig. l, the reference character RT designates a stretch of railway track of considerable length designated in the drawing for illustration purposes as of a length of the order of 50 to 100 miles. The invention is, of course, not limited to any specific length of track. The track RT may be a single track line or it may be one track of a multiple track railway. I shall assume that track RT is an eastbound track of a multiple track road and a train shown convetnionally at TN is en route eastbound over the stretch and the train TN has at least one vehicle provided with communication equipment.

The dot and dash rectangle WS designates a wayside station located at some intermediate point along the stretch of railway, and as here indicated the wayside station is located substantially at the mid point of the stretch for which communication is desired.

The train TN and wayside station WS are provided with two-way communication equipments, each of which includes a transmitter TA and a receiver RA. The transmitter and the receiver of the train and station are preferably similar and each is shown conventionally for the sake of simplicity since the specific structure of each of these devices forms no part of my invention and each may be any one of several well-known arrangements. For example, the transmitter and receiver may be similar to those described in Letters Patent of the United States No. 2,064,639, granted December 15, 1936, to Leland G. Whitelock et al., for Communicating Systems, or to the arrangement disclosed in my copending application for Letters Patent of the United States, Serial No. 575,311, filed January 30, 1945, for Railway Train Communication Systems, and now PatentNo. 2,484,680, granted October 11, 1949. It is sufficient forthe present application to point out that the transmitter and receiver use a carrier current, a carrier of the same frequency being preferably used for transmission in both directions. For example, the carrier would preferably be one having a frequency selected from the to 250 kc. band. It is also to be noted that each equipment includes a directional means wherewith the receiver is deenergized or desensitized duringperiods the transmitter at the same location is sending.

g The reference characters LI and L2 designate a pair of line wires extending along the railway. These line wires would be carried on the usual pole line and would extend substantially parallel to andreasonably close to the track RT. That is, line wires LI and L2 extend continuously throughout the territory covered by the communication system and are at all times within inductive range 4 of the track. This pair of line wires may be those used in existing telegraph or similar service and are used for train communication as an additional service without interference with their present use. The line wires LI and L2 may be Wires installed for train communication only.

The line wires LI and L2 in multiple, their distributed impedance to ground and the ground path, form a longitudinal circuit which is included in the transmitting channel for the communication system and with which channels train carried circuit elements are inductively associated. This transmitting channel for railway train communication is explained and covered in my Letters Patent of the United States No. 2,064,642, granted December 15, 1936, for Railway Train Communication Systems. It is sufficient for the present application to explain that the transmitter TA of the train TN is preferably coupled to a sending circuit having connection to two pairs of spaced Wheels of the train so that the communication current supplied by the transmitter TA flows in the rails between the two pairs of wheels and a corresponding voltage drop is developed across this length of the rails. This voltage causes current to flow in a circuit including the rails each side of the train, the distributed rail to ground impedance and ground, and energy is transferred from this circuit to the line wires LI and L2 in multiple due to the distributed inductance of the line wires and the rails. Energy is also transferred to the line wires by the mutual induction between the transmitting connections to the vehicle Wheels, the rails beyond the vehicle, and the line wires. Such transfer of energy to the line wires causes in turn the carrier telephone current to flow in the longitudinal circuit of the line wires. The receiver RA of the train is connected to a pick-up coil PC mounted on the train for inductive relationship to the transmitting channel so that the carrier telephone current flowing in the longitudinal circuit of the line wires and flowing in the rails induces a corresponding electromotive force in the pick-up coil and this electromotive force is applied to the receiver RA.

At the wayside station the transmitter TA and receiver RA are connected across the transverse circuit of the line wires LI and L2 through a coupling unit CU. A transformer T3 of the coupling unit CU is provided with a primary winding ID connected to the output of the transmitter TA and with a secondary winding I I, one terminal of which is connected to the line wire L2 through a blocking capacitor I2 and lead wire I3, and a second terminal of which secondary winding is connected to line wire LI through a blocking capacitor I4 and lead wire I5.

The input of the receiver RA is connected across the line wires LI and L2 in multiple with the secondary winding II of the output transformer T3, additional blocking capacitors I6 and I! being preferably interposed in the connection to the receiver.

The blocking capacitors I2 and I4 are proportioned to pass the carrier telephone current but to block direct current and low frequency currents that may be used for telegraph and similar circuits of the line wires. The blocking capacitors I6 and I! are provided to further protect the input of the receiver.

Thus a carrier telephone current supplied by the transmitter TA at the wayside station is applied to the transverse circuit of the line wires and a telephone current flowing in the transverse is thus available'for effectively influencing train carried receivers. Conversely, carrier telephone currentsupplied by the train carried transmitter of-FigiZ applies energy to the longitudinal circuit andwhich energy is transferred from the longitudinal circuit to the transverse circuit at location A3 for transmission to the wayside station WS over the transverse circuit. Although I have herein shown andv described but two forms of means for increasing the range of inductive train communication systems embodyin'g my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention. I

Having thus described my invention, what I claim is: V

1. In means for increasing the range of communication of a train communication system, the combination comprising, a stretch of railway track which has a length of the order of four times a given effective range of communication, a train to travel said track, a wayside station located at approximately the mid point of said stretch, two communication equipments one mounted on said train and one located at said station; each said equipment including a transmitter'and a receiver of a given carrier communication'current, a pair of line wires extending the full length of said stretch and disposed substantially parallel to said track, said pair of line wires adaptable of being used in a transverse circuit which includes the two wires in series and in a longitudinal circuit which includes the two wires in multiple and the ground path, means at said station to connect the station communication equipment across said line wires to supply and receive the carrier communication current to and from said transverse circuit, circuit elements mounted on said train, said circuit elements connected to said train communication equipment and disposed for inductive relationship with said line wires in multiple to supply and receive the carrier communication current to and from the longitudinal circuit, two transfer means one located each side of the station, each said transfer means located at a point preselected between the station and the remote end of the stretch on the same side of the station, each said transfer means including a transformer having a first and a second winding, and each said first transformer winding connected across said line wires and each said second transformer Winding 8. connected between the line wires in multiple and ground for each said transfer means to be efiective to transfer. the carrier communication current between the transverse circuit and the longitudinal oircuit'and vice versa.

2. In means I'orincreasing the range of communication between trains operating over a stretch of railway track and the wayside when the stretch is of a length of the order of four times the efiective communication range of a two-way communication equipment having a given power output, the combination comprising. a stretch of railway track, a train which travels the stretch, a wayside station located at approximately the mid point of said stretch, two-way carrier communication equipments having a give en power output one mounted on said train and one located at said station, a pair of line wires extending along the full length of said stretch, said pair of line wires capable of being used in a transverse circuit which includes the line wires in series and in a longitudinal circuit which includes the line wires in multiple and the ground path, circuit means at said station including capacitance to couple said station equipment to the transverse circuit, circuit elements mounted on said train for inductive relationship with the longitudinal circuit and connected to said train equipment, two transfer points one located each side of the station approximately halfway between the station and the far end of said stretch on the same side of the station, a current transfer means including a transformer having independent flrst and second windings located at each of said transfer points, a first circuit means including capacitance at each said transfer point to connect the first transformer winding at the same point to said transverse circuit, and a second circuit means including capacitance at each said transfer point to connect the second transformer winding at the same point to said longitudinal circuit.

PAUL 'N. BOSSART.

' REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,803,453 Affel May 5, 1931 2,124,709 Phebus July 26, 1938 2,240,676 Shaver May 6, 1941 

